In an image forming apparatus such as a laser printer, an electrostatic latent image is formed on the surface of a photosensitive drum. The electrostatic latent image is developed by a toner, so that a toner image is carried on the surface of the photosensitive drum. The toner image is transferred to a sheet, thereby achieving image formation on the sheet. Such an image forming apparatus includes a developing apparatus for feeding a toner to the photosensitive drum.
The developing apparatus includes a developing tank accommodating a developing roller, and a toner cartridge set on the upper portion of the developing tank for supplying the toner into the developing tank, for example. The toner cartridge is provided with an agitating member for agitating the toner. The toner accommodated in the toner cartridge is agitated by rotation of the agitating member, and fed into the developing tank from the toner cartridge.
In order to prevent the agitating member from continuously stopping while resistance is applied by the toner in this type of developing apparatus, proposed is a technique of detecting the position of the agitating member with a reflection- or transmission-type photosensor and stopping the agitating member on a position where the toner applies a less load to the agitating member.
If a sensor for detecting the position of the agitating member is independently provided, however, the number of components is increased as compared with the conventional developing apparatus, to disadvantageously increase the cost for and the size of the developing apparatus.